1. Field of the Invention
The present invention generally relates to a carrying apparatus for carrying a sheet-like carried medium, particularly a carrying apparatus, an image forming apparatus, a carried medium carrying method, and a computer readable medium storing a computer program which enable control of a rotational speed of a carrying rotational measure for carrying the carried medium.
2. Description of the Related Art
An example of an image forming apparatus transfers a toner image formed on an intermediate transferring belt or a photoreceptor drum to a recording paper in a transferring unit, and then fixes the toner image to the recording paper. In the transferring unit, the transferring roller presses the recording paper against the intermediate transferring belt or the photoreceptor drum. There is a fuser device on a downstream side of the transferring unit. When the size of the recording paper becomes a predetermined size or more, the recording paper reaches the fuser device while the recording paper is interposed between the transferring roller and the intermediate transferring belt. Since the rotational speed of the fuser roller of the fuser device and the rotational speed of the transferring roller are separately controlled, when the recording paper bridges the transferring roller and the fuser roller, the recording paper may be pulled by the fixing device or pushed by a secondary transferring roller to exchange torque due to a slight difference between the rotational speeds of the transferring roller and the fuser roller.
When the torque is exchanged between two rollers, an image quality is deteriorated or a color shift may occur due to a slippage of any one of the rollers. Specifically, when the weighting capacity, i.e. the weight per unit area, of the recording paper is large like a dense recording paper or a thick recording paper, the recording paper may be slipped by pushing of the recording paper when the circumferential velocity of the roller on the upstream side is higher than the circumferential velocity of the roller on the downstream side.
Patent Document 1 discloses an image forming apparatus which corrects the rotational speed of a fuser roller each predetermined time using a result of comparing an appropriate loop amount with an actual loop amount.
However, in the image forming apparatus disclosed in Patent Document 1, there is a problem that the appropriate loop amount is required to be stored in advance, and a correction amount of the rotational speed of the fuser roller may depend on the appropriate loop amount. Therefore, there is no assurance that the rotational speed of the fuser roller controlled by the result of comparing the appropriate loop amount with the actual loop amount is accurate. Specifically, it is difficult to form a loop in a recording paper having a large weighing capacity.
Patent Document 1: Japanese Laid-Open Patent Application No. 2008-158076